A receptor-mediated cascade of phospholipid metabolism was analyzed. This cascade involves (a) interaction of receptors with specific ligands, (b) increased phospholipid methylation, (c) increased flux of Ca++, (d) activation of kinases, (e) phosphorylation of lipomodulin, a phospholipase inhibitory protein, (f) activation of phospholipases, (g) release of arachidonic acid and its metabolites such as prostaglandins and leukotrienes and (h) increased uptake of glucose. Lipomodulin was purified from culture media of HL60 cells and monoclonal antibodies against purified protein were isolated. This protein appeared to be associated with the HLA gene and was suggested to play an important role in cell-cell interactions.